fixed the speed in vertical motion of lovebug

[bootboot] / bb.asm

diff --git a/bb.asm b/bb.asm
index 4eb536e..743dc9f 100644 (file)
--- a/bb.asm
+++ b/bb.asm
@@ -175,16 +175,33 @@ main_loop:
        jnz .static_loop
 
        ; draw lovebug
-       mov di, 32000
+       mov di, (200 - 32) * 320 + 160 - 16
+       mov ax, [num_frames]
+       shr ax, 2               ; /4
+       cmp ax, 200 - 32
+       jz .end
+       mov bx, ax
+       shl ax, 8
+       shl bx, 6
+       add ax, bx
+       sub di, ax
+       call rand
+       and ax, 3               ; random value in 0, 15
+       sub ax, 1               ; random value in -3, 12
+       add di, ax
        mov si, lovebug
        call blit32
 
 ; wait for vblank
-.vsync:
+.vsync_blank:
        mov dx, 3dah
        in al, dx
+       and al, 8
+       jnz     .vsync_blank
+.vsync_visible:
+       in al, dx
        and al, 8               ; the 4th bit is 1 when we are in the vertical blanking period
-       jnz     .vsync
+       jz .vsync_visible
 
 ; copy backbuffer to video memory
        push es
@@ -201,12 +218,16 @@ main_loop:
        pop es
 
        inc word [num_frames]
+;   moved above:
+;      cmp word [num_frames], 200 - 32
+;      jz .end
 
        in al, 64h              ; 60h = keyb data port, 64h = keyb status port
        and al, 1               ; 1 = OUTBUF_FULL = the keyb controller out buf is full
        jz main_loop    ; no key pressed, loop back
        in al, 60h              ; reads the keyb that was pressed to reset the flag
 
+.end:
 ; re-enable all interrupts
        sti